A similar process and device are described in European Patent Disclosure Document No. EP-OS 0,260,331.
In the prior-art process, the workpiece layers are fed toward each other by means of conveying means. The conveying means comprise rail-guided carriages on which clamps are arranged that hold the upper end of the workpiece layers. These conveying means have track sections directed in parallel to one another in a scanning station and an aligning station. To make possible the mutual alignment of the workpiece layers, the clamps on the carriages of one of the conveying means are arranged by means of a holding head that is movable in a plurality of directions in relation to the carriage carrying it. This holding head carries a magnetizable plate that comes into frictionally engaged contact, in the aligning station, with a permanent magnet that is fastened to the adjacent carriage of the other conveying means. Using an adjusting device of the stationary aligning station, the movable holding head of the clamps on the first-named carriage is adjusted corresponding to the scanning result so that the two workpiece layers that are located adjacent to one another in the aligning station will reach the predetermined relative position. Due to the frictional engagement between the magnetizable plate on the holding head of one carriage and the permanent magnet on the other carriage, this relative position will be maintained when the two carriages move together from the aligning station into a subsequent processing station after alignment of the workpiece layers.
This design is relatively complicated, because it requires a holding head that is adjustable in a plurality of directions on each of the carriages of one conveying means. In addition, to adjusting the holding heads, the adjusting device must apply a considerable force to produce the specified relative position of the two workpiece layers in order to overcome the frictional force between the magnetizable plate and the permanent magnet, which must, as is explained, be strong enough to maintain the relative position, once set, between the permanent magnet and plate and consequently the aligned position of the workpiece layers.
It is assumed in the prior-art process that the workpiece layers to be brought together are already suspended on the clamps carried by the carriages of the conveying means, and the manner in which this suspension was performed is left open.